The terrorist attack in New Zealand is raising familiar questions about the Internet's role in radicalization. One question today is whether the man accused of organizing the attack on two mosques was inspired by racist ideas from the U.S. NPR's Martin Kaste joins us now. Hi, Martin.

MARTIN KASTE, BYLINE: Good afternoon.

SHAPIRO: You spent some time today reading the long document that this young Australian man posted online. NPR and many other news organizations have chosen not to share it, but what do you think our listeners ought to know about it?

KASTE: Well, it's mainly about his fear that white people in Western countries are going to be replaced by immigrants who have higher birth rates. Now, this is hardly a new idea. There've been books about this notion for decades, and the attacker's hero, apparently, in this document, is this British fascist from the World War II era. And he also says he reached his racist conclusions a couple of years ago when he, this attacker, was touring Europe, and he was shocked by how many non-white people lived in some parts of France, for example.

SHAPIRO: OK, so how does the Internet factor into this?

KASTE: Well, the tone of this document is all about the Internet. He writes it in this sort of snarky adolescent style. And especially, there's this lengthy self-interview he does, sort of imagining what the media might ask him. It's really self-important, but it's also full of all these winking references to Internet memes, and it's very self-aware. At one point, he even says that his racist project relies on, quote, "edgy humor and memes in the vanguard stage" in order to attract young people.

SHAPIRO: Can you give us an example of that?

KASTE: Well, probably the one everyone's talking about is how, when he was streaming live video during his attack, right at the start, he says subscribe to PewDiePie. Now, that sounds bizarre to the average grown-up, but you need to understand that PewDiePie is this Swedish video game-playing YouTube star, and his crown as the most subscribed to person on YouTube had been threatened by another YouTube account out of India. So for a lot of people, or some people, subscribe to PewDiePie is sort of Internet code for supporting white Europeans.

SHAPIRO: This echoes some of the things we hear from "alt-right" groups. What have those groups said in the way of reaction today?

KASTE: Well, they're kind of all over the map. It's sort of hard sometimes to understand what they - where they really stand. You know, this attacker is not easy to pigeonhole politically. He's a racist, but he also says he admires China. He cares about the environment. So when you read these "alt-right" sites, it's kind of a hall of mirrors of snark and sarcasm. But here's some reaction from the conspiracy theory news website Infowars.

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ALEX JONES: There's a whole globalist concerted effort by Soros and others to ban PewDiePie, and now this happens. PieDiePie's come out and said it's disgusting, it's sickening. He has nothing to do with it.

KASTE: Now, that's the Infowars star, Alex Jones, and he right away started talking about how this atrocity in New Zealand will be used, as he puts it, by the media here in America.

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JONES: They're going to make him into the right-wing white guy they want. But we're going to show you where he worships communist China, where he hates Christians, where he hates conservatives, and he just sounds like your standard leftist devil-worshipper.

SHAPIRO: Martin Kaste, is there any connection between what this guy writes and American politics?

KASTE: Well, none that we've seen so far; certainly no connection to any organizations that we've seen evidence for. But the attacker seems very aware of our politics, that he says he hopes that this attack will actually gin up some of the tension in our country over gun rights. And in fact, he's just admitting in another way that this is all sort of him once again trying to troll us.